The present invention generally relates to swivels for connecting fluid flow lines. More specifically, the present invention relates to hydraulic swivels having multi-component seal structures, such as labyrinth seals.
A hydraulic swivel for rotatably connecting fluid flow lines is a multi-component device with at least two ends that are connectable to fluid flow lines. In practice, hydraulic swivels usually include a female component and a male component that is rotatably inserted within the female component. Hydraulic swivels typically have a mechanism for retaining the male component within the female component, a mechanism for reducing frictional forces arising from the relative rotational movement between the male and female components, and a mechanism for sealing any annular space located between the male and female components to minimize or prevent escape of fluid from the hydraulic swivel. These mechanisms may vary somewhat, depending upon the balanced or unbalanced nature of the hydraulic swivel.
In a balanced hydraulic swivel, fluid flowing between the inlet and outlet of the swivel places substantially the same amount of force upon upstream and downstream swivel components. Thus, the fluid forces are said to be balanced and do not tend to separate the downstream components from the upstream components. In balanced swivels, retaining clips are typically adequate to retain the male component within the female component. Nonetheless, multi-component bearings are usually positioned between the female and male components to reduce frictional resistance. For example, bearing race portions may be included in facing annular surfaces of the male and female components. Bearing members, such as ball bearings, are then positioned within the race formed by adjacent race portions of the male and female components. The bearing members, in cooperation with the bearing race portions, reduce frictional force between the male and female components and facilitate relative rotational movement of the male and female components. Balanced hydraulic swivels are typically sealed to prevent fluid leakage from the swivel by inserting a polymeric o-ring between the male and female components. For example, the o-ring may be positioned in an annular recess formed in the male or female component so that the o-ring is in slidable contact with a surface of the male or female component that faces the annular recess.
In an unbalanced hydraulic swivel, fluid flowing between the inlet and outlet of the swivel places greater forces upon the downstream swivel components than upon the upstream swivel components. The swivel therefore experiences unbalanced fluid forces that tend to separate the male and female components, absent an adequate retaining mechanism. In unbalanced hydraulic swivels, bearing members that are retained in a bearing race are typically used to prevent separation of the male and female components and to minimize frictional forces between the male and female components. As with pressure balanced swivels, the bearing race may be formed by facing annular race portions that are disposed in the male component and the female component As with pressure balanced swivels, a polymeric o-ring is typically inserted between the male and female components of the swivel to prevent fluid leakage from the unbalanced hydraulic swivel.
Hydraulic swivels often operate in less than optimum conditions where the fluid flowing through the hydraulic swivel may be corrosive or may lack significant lubricating qualities. Corrosive fluids tend to chemically degrade many types of polymeric materials that are used in making many of the available o-rings, When corrosive fluids and/or fluids with poor lubricating qualities by-pass the o-ring seal, the fluid is then free to contact any bearing component of the hydraulic swivel. If the fluid is corrosive, the fluid may cause corrosion or other degradation of the bearing components that increases torque in the swivel and inhibits relative rotational movement between the male and female components. Fluid with little or no lubricating capacity also increases torque in the swivel and inhibits relative rotational movement of the male and female components, when the fluid contacts bearing components of the swivel. Furthermore, the rate at which fluid by-passes the o-ring may be adequate to wash lubricant out of the bearing race and further inhibit relative rotational movement between the male and female components.
There is a need for a new type of seal that adequately protects, or eliminates the need for, bearing mechanisms, such as ball bearings, that are presently used in hydraulic swivels. Additionally, there is a need for a new type of seal that protects bearing mechanisms from contact with corrosive and/or low lubricating capacity fluids that are carried through hydraulic swivels. Also, there is a need for a new type of sealing structure that is capable of operating for extended periods of time without degradation of the sealing qualities of the sealing structure. Finally there is a need for a new type of sealing structure that is capable of operating for extended periods of time while protecting bearing mechanisms from the effects of corrosive and/or low lubricating capacity fluids.